Carotenoid Composition And Non-Targeted Metabolomics Analysis Of Discoloration Pepper And Red Pepper

Capsicum annuum L.is a genus of the genus Solanaceae.It can produce spicy or sweet berry annual or perennial traditional vegetable crops.Capsicum annuum L.is the largest economic crop in China.first.Capsicum fruits are rich in carotenoids,which can not only give plants and flowers bright colors,but also an important indicator for measuring the appearance and color of fruits and vegetables and their intrinsic nutritional value.However,during the post-harvest drying process,especially in the natural drying process,the red part of the skin and flesh of the pepper often fades and becomes yellowish-white,forming "discoloration","white shell",and "flower peel" dry peppers,which seriously affects the sensory quality and commodity value of pepper.So far,little research has been done on the carotenoid composition and related metabolic mechanisms of discoloration peppers.Therefore,it is necessary to study the carotenoid composition and metabolism of dried peppers in discoloration,and to find the formation mechanism of dried peppers in discoloration.In view of this,this study uses Zunyi Shrimp Town Bullet Dried Chili as a test material.First,the intrinsic relationship between the carotenoid composition in discoloration dried peppers and normal red peppers and the color of discolorations is explored.Then the metabolomics analysis was used to study the relationship between the different metabolic pathways and carotenoid biosynthesis in the peels of discoloration peppers and red peppers,and to explore the formation mechanism of discoloration peppers.The main findings are as follows:1.Carotenoid composition of discoloration pepper and red pepper.Using ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry to determine the carotenoid composition in discoloration peppers and red peppers,57 types of carotene were initially identified.It was found that there was no significant difference in carotenoid composition between discoloration peppers and red peppers,but the total content was reduced by 33.63%.Among them,capsanthin esters,zeaxanthin esters and nigroxanthin esters have the largest degradation.They accounted for 45.70%,12.01% and 5.01% of the total degradation,respectively.The colorimeter was used to compare and study the effect of discoloration phenomenon on the appearance color parameters of pepper(L*,a*,b*,C*,H°,h and CCI).It was found that compared with red pepper peels,discoloration pepper peels have reduced brightness(L*),red(a*)and yellow(b*),and reduced color intensity(C*),The appearance color(H°)of the skin changes from red of red pepper to orange-yellow,and the color appearance quality(CCI)is deteriorated.The principal component analysis was used to study the relationship between the color of dried pepper peels and the carotenoid pigment composition.The results showed that the content of carotenoid esters was the main factor affecting the color of discoloration pepper.Redness and yellowness decreases,showing a "discoloration" phenomenon.2.Non-targeted metabolomics study of discoloration pepper and red pepper.Using non-targeted metabolomics of high performance liquid chromatography-high resolution mass spectrometry technology,9300 metabolite content information was obtained in discoloration pepper peels and red pepper peels,and screened out 472 differentially expressed metabolites.After KEGG enrichment analysis,it was found that the metabolic pathways with the highest metabolite expression differences between discoloration peppers and red peppers were mainly lipid metabolism,terpenoids and polyketone compounds.It is speculated that after the dry pepper is subjected to stress,the lipid metabolism in the body is dysregulated,and the fluidity and permeability of the lipid membrane are changed,leading to a decrease in the stability of carotenoids in the peel tissue of pepper and a tendency to degrade.At the same time,the accumulation of various lipids such as jasmonic acid and12-OPDA in the lipid metabolism pathway induces the carotenoids(esters)on the peel to reduce their content after exerting their antioxidant effect,so the discoloration.The content of carotenoids in pepper is significantly reduced,and the color of the peel is reduced,which makes the pepper fruits show a discoloration phenomenon.CONCLUSION: Discoloration pepper is actively responded to stress through biological processes such as lipid metabolism,terpenoids and polyketide compounds,which are affected by adversity stress,and a large amount of related metabolite content changes,resulting in lipid membrane fluidity and permeability changed,carotenoids(red and yellow carotenoids such as capsanthin,zeaxanthin,and nigroxanthin esters)in the peel were significantly reduced,so that the red color and yellow color on the pepper fruits were reduced,showing discoloration phenomenon.